Process for improving lubricating oils by hydro-refining in a first stage and then hydrofinishing under milder conditions



Y N Bmw MTW. I DT 0mm G N www Lmm AISEQ .R D1 BTL m0, ELI 1 LGFR N Et OIAWC CWMUO Lw am MGNl .T Ni E IHF RNS @wm FMI iw BOR CRD www. PH 7 5 9 1 n. 9 2 n a J United States N Patent y l PROCESS FOR IMPROVING LUBRICATING OILS `BY HYDRO-REFINING IN A FIRST STAGE AND lISZDROFINISHING UNDER MILDER CON- Edward L. Cole, Glenham, and William E. Skelton, Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware facture of lubricating oils. More particularly, it relates to a two-step process in which a lubricating oil stock is treated with hydrogen to produce an intermediate product y of improved viscosity index and this intermediate product is further treated with hydrogen to produce a lubricating oil of improved stability and resistance to oxidation. In the process of this invention, a hydrocarbon lubricating oil stock is hydrogenated at temperatures in the range of 600 to 800 F. in the presence of a hydrogenation catalyst to convert the said lubricating oil stock to an intermediate product of improved viscosity index and this intermediate product is subjected to further catalytic treatment with hydrogen at temperatures in the range of about 400 to 650 F. to produce a lubricating oil product of improved oxidation stability.

Lubricating oils are conventionally refined by methods including the steps ot' distillation, solvent refining, acid treating, clay contacting and solvent dewaxing. When residual type lubricating oils are processed, an additional step of deasphalting is usually required. In the processing steps listed above,distillation is employed as a means of separating the crude oil into fractions of suitable viscosity. Solvent refining, with, for example, furfural, sulfur dioxide or phenol, is ordinarily used as a means of removing cyclic compounds and thereby improving viscosity index of the treated oil. Viscosity index is an important characteristic of a lubricating oil indicative of the resistance of the oil to change in viscosity with change in temperature. Acid treating is employed to improve the color, stability and resistance to oxidation of lubricating oils. Clay contacting is used to further irnprove the color and to neutralize the oil after acid treating. Solvent dewaxing is used to lower the pour point of the oil, and deasphalting is employed to remove asphaltic bodies.

All of the characteristics noted above, that is, viscosity range, viscosity index, color, stability, resistance to oxidation, pour point and freedom from asphaltic bodies are important. The requirements of various lubricating applications differ greatly so that different oil characteristics may be limiting when manufacturing lubricating oils for different applications. Therefore to obtain a satisfactory lubricating oil, a balance of various characteristics is necessary depending upon the requirements of the intended application.

Mild hydrogenation of lubricating oil stocks is known in the prior art as a means of refining an oil for the improvement of viscosity index. This method of refining lubricating oils has an advantage over solvent refining in that the yields of treated oil are much higher for the mild hydrogenation process. The present process is an improvement over prior processes for refining lubricating oil by mild hydrogenation. We have found that lubricating oil stocks refined by mild hydrogenation for the improvement of viscosity index may be further treated with hydrogen under conditions less severe than ordinarily used for mild hydrogenation to produce a lubricating oil of unexpectedly good stability and resistance to oxidation.

The first step of the process of this invention, mild hydrogenation, is employed to produce significant improvement in oil quality as measured by mass units, for example, viscosity index and carbon residue. This treatment is accompanied by some splitting which produces light ends, a reduction in viscosity andlconsumption of varying amounts of hydrogen. For simplicity this step will be referred to hereafter as hydrorefining.

The second stage hydrogen treatment in contrast results in little or no change in viscosity, negligible consumption of hydrogen and little reduction in the flash point. This step will be referred to hereafter as hydrofinishing.

The hydrorefining step may be carried out employing a wide range of operating conditions and catalysts. Forl example, temperatures of about 600 to 800 F., pressures of about 500 to 10,000 p. s. ing. and space velocities from about 0.1 to 5.0 may be used. ln a preferred embodiment of this invention, however, operating conditions comprising temperatures of 625 to 725 F., pressures of about 3,000 p. s. i. g. and space velocities of about 1.0 to 2.0 volumes of oil per hour per volume of catalyst are employed. Hydrogenation catalysts comprising metals of the 6th and 8th groups of the periodic table, their oxides, suldes, or mixtures thereof may be employed in the hydrorelining step of this invention. We have found that a nickel sulfide-tungsten sulfide catalyst having a composition represented by the empirical formula lNiS-0.75WS2 and cobalt molybdate are particularly suitable for the process of this invention.

The hydrofinishing step of this process is conducted under much milder conditions than employed in the hydrorening step. Temperature and pressure are relatively low for example, about 400 to 650 F. and 750 to 5,000 p. s. i. g., respectively. Hydrogenation catalysts suitable for use in the hydrorefining step are also satisfactory for the hydrofinishing process. However, we prefer Raney nickel, platinized charcoal, cobalt molybdate and composite catalysts comprising alumina, platinum and combined halogen for the hydrofinishing step of our process.`

Other lubricating oil refining processes may be employed with the two stage process of this invention either before the hydrorefining step, between the two steps, or after the hydronishing step. However, in any series of processing steps, we prefer the hydrorening step to precede the hydrofinishing step. It is also desirable in some` cases to fractionate the hydrorened intermediate product and to hydrofinish only selected fractions thereof.

An advantage of this process is that it produces lubrieating oils of high viscosity index and unexpectedly good stability and resistance to oxidation.

Another advantage of this process is that it accomplishes product quality improvement comparable with that obtained with the three steps of solvent refining, acid f treating, and clay contacting employed in conventional refining of lubricating oil stocks.

Another advantage of the process of this invention is that it produces high yields of lubricating oils and avoids4 the yield losses inherent in solvent refining and acid treating.

The accompanying drawing diagrammatically illustrates the process of this invention. Although the drawing illustrates one arrangement of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus or material described.

A lubricating oil stock-from external storage 1 is 2 by pump 3. Hydrogen-rich gas,

charged through line from line 4 is combined with the lubricating oil stock and Patented Jan. 29, 1957'LVA the combined feed is heated" in preheater 5. The preheater efuent is passed through linev 6 to reactor 7^. Reactor 7 is operated under hydrorening conditions and contains a hydrogenation catalyst, for example, nickel sulfide-tungsten sullide. Eiiluent from reactor7` is cooled in heat exchanger 8 and' discharged into gas: separator 9. Hydrogen-rich gas' from separator 9 isk withdrawn through linev 10 and is recycled by compressor 11` through hydrogen recycle line 4. Make-up hydrogen from an externaly source, not shown, isisupplied to the unit through line 12 which discharges into recycle line 4'. A stream of recycle gasmay be withdrawn through purge gas line 13 in order to maintain the hydrogen concentration of` the recycle gas.

Liquid from gas separator 9r is withdrawn through line 14L and directed to fractionator 15. Fractionator 15 is employedl to separate the small amount of gas and distillate which are produced as a result ofA splitting reactions encountered in hydrorefining. Gas is` withdrawn through* line 16 and distillate through line 17 for utilization of' these streams in other facilitiesnot shown. The bottoms product from fractionator 15 is a hydrorelined uoride, and 98.7 weight percent alumina. Tests on thehydroiinished product are shownI in column C of Table I.

The ASTM oxidation test D943-53T and the heat test 5 in this and all other examples are run on inhibited samples containing 0.300 Weight percent of methyl ditertiarybutyl phenol, .015 weight percent alkenyl suc-*1 cinic acid, .0025 weight percent monoand di-lauryl acidI ortho phosphate' and 0.0005 weight percent phenol.

The heat test reported is a stability test in which. an

oil sample, copper wire and iron wire,y are placed in a bveaker and heated in an oven at 225 F. for 100'h'ours; The appearance of the4 oil at the end of this test is reported as the heat test.

Column B of Table I showsv the yield losses encountered in the conventional refiningA of lubricating oil stocks by solvent refining and acid treating. Column C shows that the hydrotinishing step is accomplished withoutfurther yield loss.`

Comparing columns B and` C, the increase from 1320 to 1900'hours ir. theASTM" oxidation test shows that the hydronishing step results in an improvement in the stability ofthe treatedl oil'.

Tablefl;

A B C D.Y E F Conventlon'- Bydronished, Hvdro- Convention- H'ydrotinished Lubricating ally Refinedy Convention refined ally Finished Hydrorefned Oil Charge t Lubricating ally. Refined Lubrieat- Hydrorefined Lubricating;

Stock Oil Stock Lubricating ing Oil Lubricating Oil Stock OiliStocl:v Stock O'il Stock Yield; Volume Percent Rn Rn 93.2 91.0; 93.2.

Charge. Color, ASTM'. 4minus. 1 humus..-" lminus .Watcr White, Viscosity Index minus 3. 25.5. 22.5.-. 32.5. 28 35.5; ASTM Oxidation T t Unsatisfactory.. 1,320 1,000 r6150 825 2,875;

D943-53I,` Hoursv to, 2 Neut.y No.1v4 v Heat Test l-- do Darker Unchanged.

1 Inhibitedoil.

lubricating oil stock of improved viscosity index; This 4,3

intermediate product is withdrawn through line 18 and is combined with recycle hydrogen from line 19 and passed; to preheater 20. Eiiiuent from preheater 20 isv transferred through line 21 to reactor 22. Reactor 22 isoperated under hydronishing conditions and contains a hydrogenation catalyst, for example, cobalt molybdate. Product from reactor 22 is withdrawn through line 23, cooler 24 and is discharged into gas separator 25.

vHydrogen-rich gas from gas separator 25y is withdrawn EXAMPLE I' Tests' on anl 18.8""v API gravity lubricating oil stock are shown in Tablev I, column A and show poor color, viscosity indexand' unsatisfactory stability.- Thisoil is conventionally relined for viscosity index and color improvement by solvent refining, acid` treating and clay percolation to produce a lubricating oil stock with the results shown in-` column B. The solvent reiinedL acid 'treatedi andV clay--percolated lubricatingy oil of column B i'stheni further reiined under hydronishing conditions by contacting with hydrogen at 500 F., 3,000 p. s. i.',g'. pressure in the presence of a catalyst comprising, 0.5

Weight' percent' platinum, 0.8Wei`ghtLpercent'aluminum;

The lubricatingV oil stock shown in column A of Table I isf alsoV refined by` treating under hydroreiiningV conditions to produce a lubricating oil stock with the results shownV in` column D of Table I.

In this example, the

hydroreiining conditions employed comprise contacting.l

the oil with hydrogen at a temperature of 690 F'., a

pressure of 3,000 p. s. i. g., a` volumetric space velocity of 1.97 volumes-'ot` oil per hour per volume of catalyst,v in thepresenceof a nickel sulfide-tungsten sulfide catalyst having a composition represented by the empirical f formula liNiS-OJSWSZ. The hydrorefined lubricating oil stock shown. in column D is finishedby the conventional refining stepsv of acid treating, water washing, neutralizing, steaming, brightening by air blowing, and finally clay percolation to produce the finished lubricating oil with theA results shown in column E of Table I.

Comparisonofcolumn B with column` D shows that an oil of higher viscosityindex is obtained by hydroreiiningf than by conventional reiining for the improvement ofv thisl characteristic. However, it will be noted that poorer resistance to oxidation is exhibited by conventionally finished hydroretined oil, column E, as compared with the processing sequence of conventional reiining followed by hydrofinishing, columnC.

In a test employing the process of this invention, that is, hydrorefining followed by hydroinishing, the hydroretined lubricating oil stock shown in column D is'hydro finished by contacting with hydrogen at 500 F., 3,000' p. s. i. g. pressure in the presence of a catalyst comprising 0.5 weight' percent platinum, 98.7 weight percent alumina' and 0.8 weight percent aluminum fluoride.

Tests on the hydrofinished', hydroreiinedlubricating oil are. shown in columnl F. Column F shows that an oil or unexpectedly goed stability and resistance tooxidation, is produced by hydroretining following by hydroi'inishing, and` that the oilprod'uceclis superior tothe conventionally refinedandz hydroinished oil shown in column C or the hydrorened and conventionally nished oil shown in column E. It will also be noted that a higher yield of finished oil is obtained by hydrorefining followed by hydronishing.

EXAMPLE II The lubricating oil charge stock employed in Example I is hydrorened using a nickel sulfide-tungsten sulfide catalyst and hydroiinished using a catalyst comprising platinum, aluminum fluoride, and alumina under the conditions and with the results shown in Table II.

Table Il Hydrorening:

Reactor Temp.,F 690 621 650. Recycle Hydrogen Ratio, 10,000. 10,000. 10,000.

cu.lt./bb1. Pressure, p. s. Lg 3,000 3,000 3,000. Liquid,v./v./hr 1.6.. 1.0 1.0. Yield, Vol. Percent, Charge.. 91.8 86.7. Hydrorened Product:

Viscosity Index 4 17.5 36.5. ASTM Oxidation Test,

29413-5311 Hours to 2 N eut.

o. Heat Testl Darker- Hydronishing Conditions:

Reactor Temp.,F 500 500 500. Pressure, p. s. i.g 3,000 3,000 3,000. ield, Vol. Percent, Charge.. 90.0 91.8 86.7. Color, ASTM Water Water Water White White White. Viscosity Index 43.0 24.0.... 38. ASTM Oxidation Test, 3,000... 2,0G0 2,850.

1139413431 Hours to 2 Neut.

o. Heat Test1 Un- Un- Unchanged. changed. changed.

1 Inhibited oil.

Table II shows that an oil of exceptional oxidation resistance and heat stability is produced by the process of this invention, that is, hydroreiining followed by hydrofinishing.

EXAMPLE III In another test, a lubricating oil stock is hydroreiined using a nickel sulfde-tungsten-sulfde catalyst at a temperature of about 650 F. and at a pressure of 3000 p. s. i. g. A sample of the hydroretined oil is applied to an aluminum disc which is then heated at a temperature of 644 to 680 F. for thirty minutes. At the end of this heating period the aluminum disc is found to be stained. The hydroreiined lubricating oil is hydronished at a temperature of 500 F., a pressure of 3000 p. s. i. g. employing a Raney nickel catalyst. A sample of the hydroretned and hydroiinished lubricating oil is applied to an aluminum disc and heated at 644 to 680 F. for thirty minutes. The aluminum disc is found to be free of stain. This test indicates that the hydrolinishing step has improved the stability of the oil so that aluminum is not stained in contact with the oil at high temperature.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of processing a hydrocarbon lubricating oil stock to enhance the quality thereof which comprises subjecting said lubricating oil stock in admixture with hydrogen and in the presence of a hydrogenation catalyst to conditions of mild hydrogenation such that said lubricating oil stock is converted to an intermediate product of improved viscosity index, and subjecting said intermediate product in admixture with hydrogen and in the presence of a hydrogenation catalyst to a temperature of about 400 to 650 F., a pressure of about 750 to 5000 p. s. i. g. and for a time such that said intermediate product is converted to a lubricating oil of improved oxida-l tion stability.

2. The method of claim 1 in which the catalyst employed in processing the intermediate product is selected from the group consisting of nickel and platinum.

3. A method of processing a hydrocarbon lubricating oil stock to enhance the quality thereof which comprises subjecting said lubricating oil stock in admixture with hydrogen and in the presence of a catalyst comprising nickel sulfide and tungsten sulfide to a temperature of 625 to 725 F., a pressure of about 3,000 p. s. i. g. and a space velocity of about 1.0 to 2.0 volumes of oil per hour per volume of catalyst to convert said lubricating oil stock to an intermediate product of improved viscosity index, and subjecting said intermediate product in admixture with hydrogen and in the presence of a catalyst comprising platinum, alumina, and a combined halogen to a temperature of about 400 to 650 F., and a pressure of `about 1000 to 5000 p. s. i. g. to convert said intermediate product to a lubricating oil of improved oxidation stability.

4. The method of processing a hydrocarbon lubricating oil stock to enhance the quality thereof which comprises subjecting said lubricating oil stock in admixture with hydrogen and in the presence of a hydrogenation catalyst comprising cobalt molyhdate to conditions of mild hydrogenation, such that said lubricating oil stock is converted to an intermediate product of improved viscosity index and subjecting at least a portion of said intermediate product in admixture with hydrogen and in the presence of a hydrogenation catalyst to a temperature of between 400 and 650 F., a pressure of between 750 and 5,000 p. s. i. g. and for a time such that said intermediate product is converted to a lubricating oil of improved oxidation stability.

5. The method of processing a hydrocarbon lubricating oil stock to enhance the quality thereof which comprises subjecting said lubricating oil stock in admixture with hydrogen and in the presence of a hydrogenation catalyst comprising nickel sulfide and tungsten sulde to conditions of mild hydrogenation, such that said lubricating oil stock is converted to an intermediate product of improved viscosity index and subjecting at least a portion of said intermediate product in admixture with hydrogen and in the presence of a hydrogenation catalyst to a temperature of 400 to 650 F., a pressure of between 750 and 5,000 p. s. i. g. and for a time such that said intermediate product is converted to a lubricating oil of improved oxidation stability.

6. A method of processing a hydrocarbon lubricating oil stock to enhance the quality thereof which comprises subjecting said lubricating oil stock in admixture with hydrogen and in the presence of a catalyst comprising cobalt molybdate to conditions of mild hydrogenation, such that said lubricating oil stock is converted to an intermediate product of improved viscosity index and subjecting at least a portion of said intermediate product in admixture with hydrogen and in the presence of a catalyst comprising platinum, alumina and a combined halogen to a temperature of 400 to 650 F., and a pressure of about 1,000 to 5,000 p. s. i. g. to convert said intermediate product to a lubricating oil of improved oxidation stability.

7. The method of claim 6 in which the combined halogen is aluminum fluoride.

References Cited inthe tile of this patent UNITED STATES PATENTS 2,413,312 Cole Dec. 31, 1946 2,542,471 Brandon Feb. 20, 1951 2,706,167 Harper et al Apr. 12, 1955 2,718,490 Porter Sept. 20, 1955 2,719,108 Porter Sept. 27, 1955 

1. A METHOD OF PROCESSING A HYDROCARBON LUBRICATING OIL STOCK TO ENHANCE THE QUALITY THEREOF WHICH COMPRISES SUBJECTING SAID LUBRICATING OIL STOCK IN ADMIXTURE WITH HYDROGEN AND IN THE PRESENCE OF A HYDROGENATION CATALYST TO CONDITIONS OF MILD HYDROGENATION SUCH THAT SAID LUBRICATING OIL STOCK IS CONVERTED TO AN INTERMEDIATE PRODUCT OF IMPROVED VISCOSITY INDEX, AND SUBJECTING SAID INTER- 